Pulse radar system



D. E. KENYON PULSE RADAR SYSTEM prii l2, 1949.

3 Sheets-Sheet 1 Filed Jan. 18, 1944 Apri l2, i949. D. E. KENYON I PULSE RADAR SYSTEM www 3' Sheets-Sheet 2 Filed Jan, 18, 1944 TIME O AZIMUTH MAI N GATE VOLTAGE LEADENG GATE VOLTAGE Fics@ MAKER mvENToR Y DAVID E. KENYON 4 BYL/ pr E2, 1949. D. E. KENYON ZASSQZH l PULSE RADAR SYSTEM Filed Jan. 18. 19.44 l 3 Sheets--Sheet 3 3 a5 z8 l ,i- D

'mr n. v n-l- Z 5S INVENTOR g DAvlD E. KENYON BY gw #my ORNEY .employed as indicators.

Patented Apr. 12, 1949 David E. Kenyon,

The Sperry Corporation,

ware

smith'town, N. Y., assignor to a corporation o! Dela- Application January 18, 1944, Serial No, 518,678 7 Claims. (Cl. 343-13) The present invention relates to radio locator systems or radar systems, particularly, such systems of the type producing indications on a screen.

An object of the invention is to provide an improved range indicator for object locating systems.

More specifically an object is to improve the linearity of range indications at short range.

Furthermore, it is an object of the invention to provide methods and apparatus for insuring the presence of the 4zero marker, as well as succeeding short range markers on the indicator screen.

In certain types of object locating apparatus, cathode ray tubes with fluorescent screens are Graphic indications are produced on the iiuorescent screenl by the defiection of the cathode ray beam vof the tube. Characteristic bright markers on the fluorescent screen are utilized instead of an external or printed scale for determining distances along an axis, usually the vertical or range axis. Such markers are produced by means of a marker generator acting upon the intensity of the cathode ray beam and producing screen at. predetermined intervals corresponding todeflection of the beamaiong the axis in question. A square wave voltage or cathode ray gate voltage, as it is customarily called, is employed for energizing the cathode ray tube during the period of time that indications are expected to .be produced. In order to sweep the beam along vthe vertical, or rangeaxis, a triangular sweep wave generator is provided.'y A

In the case of objects located at very short range so that only a short period of time elapses beforeindications are'. produced on the screen, difculty may be encountered from thefact that thecathode ray gate voltagev may not rise promptly to a suiiibient value to energize the cathode ray tube and from the fact' that the initial portion of the triangular current wave produced by the sweep wave generator is ordinarily not linear, In consequence, the zero marker may be lost and nonlinear indications of close ranges are produced. It is accordingly an object ofthe-invention to provide methods and apparatus for avoiding the loss of the zero range marker and the initial markers before the cathode ray tube has been sensitized, and it is an object to provide methods and apparatus for insuring linearity ofthe indication for short ranges.

An object of the invention is to insure that the bright vmarkers Aon the cathode ray tube is in satisfactory condition to receive zero range markers and succeeding short range signals by delaying the marker impulses and video signals long enough for the cathode ray gate voltage to build up and for the vertical sweep to become linear. b Other and further objects and advantages will become apparent as the description proceeds.

In carrying out the invention in its preferred fo'rm a conventional type of radio locator apparatus may be employed, such as an azimuth sweep system, for example, employing a pulse transmitter, a suitable receiver including a video amplifier, and a cathode ray tube with horizonr range indications,

er input to the cathode ray tube are delayed by tal and vertical sweep circuits and a control grid responsive tc the output of the video amplifier in order to produce spots on the screen whenever a signal reflected from the detected object is received by the receiver. A conventional marker generator synchronized with the transmitted pulses may also be coupled to the grid of the cathode ray tube for producing range markers. In order to insure the presence of the zero range markers and to produce linearity of short the video signal and the markinterposing a wide band delay line in the connection from the marker generator and the video amplifier to the cathode ray tube control grid.

A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanyv ing drawings in which, Fig. 1 is a schematic gram of one embodiment of my invention;

Fig. 2 is a diagram illustrating the appearanceof the screen of the cathode ray tube and explaining the principle of operation of the invention;

Fig. 3 is a graph illustrating the relationship "between current and time in the sweep circuit including the vertical deecting coils of the cathode ray tube;

Fig. 4 is a fragmentary diagram of an embodiment of the invention in which a delay cable is employed; l

Fig. 5 is a fragmentary circuit diagram of an arrangement in which a leading gate is employed for producing the delay in the input to the control grid of the cathode ray tube;` and Fig. 6 is a graph explanatory of the principle of operation of the apparatus of Figf5.

Like reference characters are utilized throughout the drawing to designate like parts.

and electric circuit dia-i In microwave pulse type object locators, objects are detected by directing a series of pulses of microwave radiant energy in the direction in which the possible existence of an object is suspected and observing whether or not any pulses are returned, thus indicating the presence of an object serving to reflect the transmitted pulses. The apparatus for transmitting the microwave pulses and for receiving the reflected pulses is pivotally or rotatably mounted so as to scan an area which is to be patrolled, or In which objects are to be located. The location of the object is then determined by determining the angular position of the scanner at the instant when the reflections are received. In locators of the azimuth-sweep (or ASD) type, the horizon is scanned and indications of azimuth and'range of a detected object are produced upon the same screen.

For indicating the location, an indicator of the cathode ray tube type may be employed in which reected pulses produce luminous marks on the screen and the cathode ray beam is swept across the screen both vertically and horizontally in order to scan the entire surface. The beam is swept horizontally across the screen in accordance with the sweeping or scanning motion of the scanner so that the positions on the screen of the indications of reflected signals serve as indications'of the angular positions of the detected objects. The beam is also swept vertically along the screen to represent distance or range. In order that stray magnetic fields and the position of the apparatus with respect to the earths magnetic eld will not affect the scale calibration by virtue of magnetic action on the cathode ray beam, as well as for other reasons, electrically produced range marker indications are used on the scale instead of an external or permanently printed or/ engraved scale on the screen.

Such a system is represented schematically in Fig. 1 of the drawings, which includes a transmitter II, a receiver I2, a common antenna or radiator I 3 for the transmitter I I and the receiver I2, and a suitable indicator such as a cathode ray oscilloscope I4 responsive to the receiver I2. For causing the scanner I3 to sweep back and forth along the horizon, a motor I5 may be mechanically connected through suitable gearing I6, to the radiator I3 shown in the form of a paraboloid pivotally secured to a pivot shaft or axis I1. The transmitter II is assumed to be of the ultra high frequency or microwave type and a suitable transmission line in the form of a hollow pipe wave guide I8 is interposed between the transmitter II and the parabolic radiator I3. The receiver I2 may be connected to the same radiator I3 through a branch wave guide I9. For damping out direct transmission from the transmitter II to the receiver I2, a suitable radiant-energy valve, blocking or power-limiting device 2I may be provided, which is herein referred to as a TR box. TR boxes are described in the copending applications of Eric J. Isbister, 509,061, filed November 5, 1943; Joseph Lyman et al., 406,494, filed August 12, 1941; Wilmer L. Barrow et al., 466,530, ledNovember 20, 1942, now Patent No. 2,454,761, issued November 30, 1948. Each of these applications shows a TR box comprising a cavity resonator containing an ionizable gas medium and employed as a coupling device between a receiver and a radar antenna to which a radar pulse transmitter is coupled. When weak signal energy reected from a distant object is intercepted by the antenna, the gas is not ionized, and

the resonator serves as an elcient high-Q coupling to the receiver for the intercepted energy. When a high-tensity pulse is applied to the antenna by the transmitter, on the other hand, the resonator is so strongly energized that the gas therein is ionized, with the result that the resonator Q is greatly diminished and the resonator serves as a very effective attenuator, so that the receiver is afforded protection against the strong pulses.

The'receiver I2 may include conventional elements heretofore known, such as a local oscillator 22, a crystal mixer or rst detector 23, an intermediate frequency amplifier 24, a second detector or video detector 25, and a video amplifier 26. For making the receiver responsive only during theperiod of time that reflected signals are expected to be received, a square wave generator 21, or gate generator, as it is sometimes called, is provided for supplying a voltage gate to the intermediate frequency amplifier 24. The intermediate frequency amplifier 24 is providedI with a suitable control terminal or channel 29 which serves to control the amplification thereof.

In case the intermediate frequency amplifier 24 is of the type employing one or more stages of vacuum tubes, the terminal 29 may be one through which the screen grid or plate voltage supply is obtained by the intermediate frequency amplifier 24. The control of amplification by a supply of adjustable voltage to the screen grids or plate elements of vacuum tubes is not my invention per se and therefore the internal circuit of the intermediate frequency amplier 24 need not be shown.

The cathode ray indicator tube I4 may be of a conventional type comprising a fluorescent screen 3|, a cathode 32, anodes 33 for connection to a positive voltage source (not shown), focusing electrodes or anodes 34, and a control electrode or grid 35. For deecting a cathode ray beam 36 emanating from the cathode 32 and impinging on the screen 3| suitable deflection elements are employed, such as deflecting plates or coils. In the arrangement illustrated, there is a pair of deflecting coils 31 for producing deflection of the beam 36 along a horizontal axis and there is a pair of deflection coils 38 for producing deflection of the beam 36 along a vertical axis. In the arrangement assumed, the horizontal axis represents azimuth and the vertical axis represents range. It will be understood, however, that my invention is not limited to the precise arrangement illustrated and described, nor is it limited to an arrangement in which indications are produced in azimuth instead of in elevation, or in which indications are produced in only one dimension instead of both azimuth and elevation.

For sweeping the beam 36 along the screen 3l as the radiator I3 moves in azimuth, a triangular voltage generator 39 may be provided. For the sake of illustration, the generator 39 is represented as comprising a potentiometer energized by a battery 4I and having a tap 42 mechanically connected to the radiator I3 and electrically connected through a conductor 43 to the azimuth deflection coils 31.

For sweeping the beam 36 in a vertical direction substantially linearly with the passage of time,`

a triangular or saw-tooth Wave generator 44 of the electron tube type, for example, is connected to the vertical deflection coils 38.

` For the purpose of providing an evenly spaced succession of sharp voltage pulses to the grid 35 of the cathode ray tube I4, a conventional marker generator 45 may be employed. A marker genin case a repetition rate erator is a signal generator producing recurrent short output pulses at a repetition rate which ordinarily is a predetermined integral multiple of the cathode ray tube sweep frequency. For example, with a sweep frequency of 2,000 cycles per second, a desired number n of range marker lines such as the horizontal lines illustratedin Fig. 2 may be produced on the screen of a cathode ray tube by the use of a marker generator adjusted to supply pulses at a repetition rate of 2,000 n pulses per second.

For pulsing the transmitter I I and causing the operation of the various elements of the system to be synchronized-a trigger pulse generator 46 is provided. The trigger pulse generator 46 may -be arranged to produce a succession of short time duration voltage pulses or spikes 41, at the frequency at which it is desired to pulse the transmitter Il, for example, 2,000 spikes per second, of 2,000 pulses per second the transmitter II. The trigger pulse generator 46 is coupled to the pulse controlling terminal of the transmitter II through a coupling or connection schematically indicated by a line 48 carrying an arrow indicating the fact that the transmitter Il receives its control impulses from the trigger pulse generator 46. The

is desired for other elements may also be coupled directly to Y the trigger pulse generator 46 for synchronization. Nevertheless, in object locating systems as manufactured, it has been found more convenient to provide a separate indicator trigger channel taken from the transmitter II represented by a line 49 in the drawing, and responsive to trigger pulses arriving through the channel 46. The channel 49 is directed toward the square wave generator 21 for controlling the instant of initiation of the square wave or sensitivity gating voltage 5| produced thereby.

The marker generator 45 may be synchronized from the output voltage 5I of the square wave generator 21 or may be arranged to provide also an inverted square gating voltage 54 of negative polarity instead of positive polarity. 'I 'he marker 45 may be synchronized therefrom through a channel 52. A schematically indicated connection 55 may be provided between the cathode 32 of the tube y I4 and the output voltage 54 of the square wave generator 21, which thus serves as a cathode gating voltage.

Means may be provided also for synchronizing the triangular wave generator 44 from the trigger pulse generator 46, forexample. through a branch channel 56 connected to the indicator-trigger channel 49.

In cases where it is necessary to be -able to identify the object located, conventional I.'F. F. (Identification Friend or Foe) apparatus 51 may be required, having an input antenna 56 and a triggering connection 59 from the trigger outputl channel 46 of trigger pulse generator 46. It is to be understood that such I. F. F. apparatus picks up a coded signal throughits antenna 58 in case the object detected is a friendly ship or the like, for the purpose of superimposing an identifying coded indication on the screen 3| of the cathode ray tube I4 in order to avoid attacking such a friendly craft.

In order to avoid loading the video amplifier 26, the marker generator 45 and the I. F. F. apparatus 51, a video cathode follower stage including avacuum tube 6| may be interposed in a connection from the elements 2 6, 45 and 51 to the control grid 35 of the tube I4. In the arrangement the square wave generator 21 illustrated, the elements 26, and 51 have output channels 28. 62 and 64. respectively, capacity coupled to an input connection such as a connection to a control electrode or grid 64 of the cathode `follower tube 6|. The tube 6| has' a cathode 65 preferably connected through a cable 66 of the coaxial type to the cathode ray control grid 35.

For negatively biasing the cathode follower control grid 64, a source of negative voltage such as a C battery 61, is provided and to prevent depressing the grid tial provided by the C battery 61, a directcurrent restorer 68 is provided comprising a rectiiler shunting a biasing resistor 69 with the cathode of the rectifier connected to the grid 64, and the anode connected to the negative terminal of the C" battery 61.

In order to delay the application of the video, marker and-I. F. F. signals to the grid 65 of the cathode ray tube I4, a wide band delay line 1I, having a suitable delay such as 3 micro-seconds, e. g., is interposed in the coupling from the elements 26, 45 and 51 to the control grid 64 of the cathode follower tube 6|. The delay line 1| is preferably of the wide band type in order to insure fidelity of transmission of the signals' from the elements 26, 45 and 51 through it, but the invention is notlimited to the use of a particular form of delay line, the same being schematically indicated in Fig. 1. The line 1I is preferably terminated by a resistor 12 having a resistance equal to the characteristic impedance of the line, and

a blocking condenser 13 may be interposed be.

tween the output of the line and the grid 64.

In order to insure wide band characteristics, y

' the line 1I may take the form of a delay cable,

such as a cable of the type disclosed in the copending application of Gerald L. Tawney. Serial 4o No. 474,400, filed February 1, 1943, now Patent No.

in accordance withthe curve 8| shown in Fig. l.

vertical direction and 2,387,783, issuedOctober 30, 1945, and assigned to the assignee of the present application, or such as disclosed by Kaliman in the Proceedings of the Institute of Radio Engineers, July 1940, pages 306 and 307.

l:The cathode ray tube I4 is shown as being of the magnetic deection type in which deflecting coils 31 and 88 are employed. It has been found that sweep wave circuits for producing the requisite gradually increasing current flow through the coils 38 have a current-time characteristic similar to that illustrated in Fig. 3

In Fig. 3 values of current are micro-seconds is plotted in a horizontal direction. Assuming that the trigger impulse from the channel 56 is applied at the time instant represented by the vertical line 14, the/current provided by the triangular wave generator 44 is built up relatively gradually at an increasing rate as represented by the portion 15 of the curve until an instant of time represented by the vertical line 16 at which the current-time curve has become substantially linear and follows a relatively straight portion 11 of the graph, after which the sweep current falls abruptly along the portion 19 of the curve.

The cathode ray beam 36 of the tube I4 is deilected vertically as represented by the curve 19 of Fig. 3, also shown to reduced scale in Fig. l. It is deflected horizontally substantiallylinearly Accordingly, lthe position of the point at which the beam 36 impinges on the screen 3| represents the azimuth of an object reflecting the received 64 below the negative potenplotted in the time duration measured in signal and the time required for the reflection to be received, which latter represents the range' in miles if the screen 3|A is provided with range vertical sweep curve 19. shown in Fig. 3. However,

a linear scale calibration is most practicable and the marker generator 45 is so arranged as to produce evenly spaced marker impulses 82. Accordingly, if the tube |4 were sensitized with sufficient rapidity by the cathode ray gating voltageY 54, a zero range marker 83, represented by dotted lines, would appear on the screen 3| shown in Fig. 2. Owing to the gradual rise along the portion 15 of the sweep curve 19, the next marker, for example, the one mile marker. would appear along the line represented in Fig. 2 by a dotted line B4, relatively close to the zero line 83.' The next range marker Would appear along the line 85 somewhat further spaced and the successive markers would be represented by bright lines 86, 81, 8B and 85 and so forth, which are evenly spaced as a result of the linear portion 11 of the curve 19 of Fig. 3. It will be observed therefore that'the zero range marker 03 and perhaps also the one mile range marker 84, might not be obtained owing to the possible delay in build up of the cathode ray gating voltage 54 land the initial portion of the the screen 3| would not be linear if the delay line 1| of Fig. 1 were not employed.

However, when the delay line 1|`is employed, the application of video signals to the grid 35 of the cathode ray tube I4 from the video amplier 26, the marker 45, and the I. F; F. apparatus 51, is delayed sufficiently so that the zero range marker is produced and appears onfa portion of the scale of the screen 3|, corresponding to the linear portion 11 of the sweep wave 13 of Fig. 3. For example, the delay may be made such that the line 85 corresponds to the zero range marker evenly spaced lines 86, 81, correspond to the successive and the successive 88, 89 and so forth,

lranges. of 1, 2, 3, 4, miles and so forth. Thus, if

objects should intercept the pulsemicrowave beam 9| at distances of 2 and 51/ miles, respectively, and at azimuth angles of approximately -30 and +45, respectively, bright areas 62 and 93 will be produced on the screen 3| land the range of the close range object 92 may be read with the same degree of accuracy as the range of a more distant object 93.

In the arrangement of Fig. 1, the delay line 1| has been shown interposed before the grid 64 of the video cathode follower tube 6|. It should be understood, however, that the invention is not limited to the precise arrangement illustrated. The requisite delay may be obtained by other means, for example, by substituting a delay cable 66 for the cable 66 shown in Fig. 1. As illustrated in Fig. 4, the delay cable 66' may be substitutedfor the cable 66 or may be interposed between the end of the cable 66 and the grid 35 ofthe cathode ray tube. In this case, the video and the I. F. F. inputs may be made directly to the grid 64 of the cathode follower tube 6|, and, if desired, the marker output channel 62 may be connected to the input end of the cable 66 or 66.

In order to obviate the expense of providing delay lines or delay cables in addition to those already employed in conventional radio locator apparatus. a leading gate circuit may be provided for producing the requisite delay in the application of video signals to the cathode ray tube. For example, as illustrated in Fig. 5, a leading gate circuit may be provided. comprising a range scale of` 8 pair of tubes |02 and |03, shown as twin trlodes, and the leading gate circuit |0| may be interposed between the main gate or square wave generator circuit 21 and the output oi the trigger pulse generator 46.

As shownin detail in Fig. 5, the trigger pulse generator 46 may take the form of a blockingv oscillator |04 having a delay line |05 interposed in its output channel 48. In the arrangement of Fig. 5, the end terminal |06 of |05 is connected to the transmitter nel |01 and to a suitable terminating impedance |08; and the delay line is tapped, for example, at a point |09 with an output channel connected to thejnput of the leading gate circuit |0|. For example, in casca nine microf second delay line |05 is employed, the tap |09 may be so positioned asto provide a delay of seven micro-seconds, thus giving a two microsecond lead to the voltage of the leading gate generator |0|.

The leading gate circuit |0| has a tube |02 split into two triode elements for the purpose `of preventing the leading gate circuit from being loaded by the output connections. For example. there may be one triode unit ||2 with an anode or output connection 55 .for supplying ya cathode-ray gating voltage 54'. Likewise, the twin tube |03 includes a triode unit I3 having an anode 4 with an output connection 56 for triggering the triangular wave generator 44. In order to avoid loading the triangular wave generator 44 and the cathode ray `gate 54", the tubes |02 and |03 are provided with second twin triode units ||5 andy ||6, respectively, which have cathodes and rcontrol grids with connections common to those ofl the units 2 and H3, respectively, The triode units H5 and ||6 are cross connected in a manner analogous to an Eccles-Jordanv trigger circuit. A coupling condenser ||1 may be connected between the anode ||8 of the unit ||5 and the grid ||9 of the unit I6, and a coupling condenser |2| may be connected between the anode |22 of the unit ||6 and the grid |23 of the unit` 5. The grids of the tube |03 are biased to ground through a resistor |24 in order that the tube |03 will be in a conducting condition. On the other hand, the grids of the tube |02 are negatively biased through a resistor |25 and a C battery |26; and the coupling condenser |2| is shunted by a voltage divider resistor |21 in order that the grids |23 of the tube |02 will normally be held below cut-01T potential by the tube |03 so that the tube |02 is normally non-conductive.

The conventional main gate circuit 21 includes a pair of tubes |28 and |29 which may be of the multi-grid type. In order to avoid loading of one output circuit by another, the tube |28 includes a negatively biased control grid |30 and a. second grid |3| with an anode output connection to the marker trigger channel 52. The tube |29 includes a control grid |32 positively biased through a resistor |33 and coupled through a condenser |34 to the second grid |3| of the tube |28, which is, in turn, coupled through a condenser |35 to the indicator trigger channel 49. The tube |29 also includes asecond grid |36 which is coupled to the control grid |30 of the tube |28 by a condenser |31 shunted by a voltage-dividing resistor |38, the grid |36 being positively biased through a resistor |39. For eliminating from the receiver the direct transmitted pulse, a short delay line such as a 0.75 microsecond delay line |4| may be interposed in the the delay line I trigger chantriggering of the leading gate l or 3 microseconds in advance ofthe leading edge ot the main gate 5|. The arrangement is such that no time constantsare required in the leadinggate. circuit the circuit being tripped on by the trigger pulse generator 43 and tripped oilby the end oi the main gate voltage produced by the main gate circuit 21. 4

Each time a trigger pulse is produced bythe blocking oscillator |04, a trigger pulse 41 is applied to the I. F. F. apparatus 31 on the channel 59. Alter a 'I microsecondtime delay (for the constants assumed by way oi illustration) a trigger pulse is applied to the leading gate circuit I0| throughthe connection and after a9 microsecond time delay, the transmitter is triggeredl by a pulse through the channel |01.

The-pulse 41 applied through the channel which is a positive pulse, raises the potential of the grid |23 of the tube |02 causing this tube to become conductive, thereby lowering the potential of the anodes producing the negative'cathoderay gate 54', or sensitizing the cathode rayl tube |4 and also depressing the potential of the grid ||9 of the tube |03 as represented by the negative square wave |45. The tube |03 is laccordingly driven non-conductive and the anodes rise in voltage abruptly producing the leading gate |43 at the anode |22 which holds the control grid |23 of the tube |02 positive, even after the trigger 41 from the trigger-pulse generator 43 has disappeared. At the same time,l the tube I3 triggers the triangular -wave generator 44, two .microseconds after the leading gate circuit 0| has been triggered; an indicator trigger 41' received through the transmitter and the channel 49 triggers the tube |23 causing it to become nonconducting and its anode voltage abruptly risesA producing the delayed sensitivity gate 5|. The anode voltage of the tube |28 has the wave shape 5|', shown in Fig. 6. The tube |20 remains non-conducting for a period of time predetermined by the time constant of the res'lstor |33 and the condenser |34, whereupon the tube |29 again becomes conducting, lowering the potential of the electrode |30, `and consequently, negatively biasing the control grid |30 of tube |23, rendering the -tube |28 non-conducting. The negative marker gate 5|' is produced by the anode of the tube |28.

For shutting oil the leading gate circuit |0|, a coupling condenser |46 is connected between the anode of the tube |28y and the'control grid ||9 oi the leading gate tube |03. When the voltage rises at the trailing edge |41 of the negative markergate 5| and the grids H9 of the tube |03 are raised in potential, the tube again becomes conducting, driving the tube |02 non-conducting and restoring all the tubes of the circuits |0I and 21 to their original condition. Thus it appears that the leading gate circuit |0| requires no timing elements and is automatically restored to its original condition by the trailing end |41 of the main gate voltage 5|' produced by the main gateA circuit 21.

Since many changes could be made in the above'construction and many apparently-widely different embodiments of this invention could be made without departing from the scope thereof, it Ais intended that all matter contained in the above description or shown in the accompanying drawings shallbe interpreted as illustrative and not in a limiting sense. What is claimed ls:

v1. An object locating system comprising in oscilloscope having a range sweep\ and a'beam control element, said receiver including a video ampliiier coupledvto said .beam control element, a range marker impulse generator also coupled to said beam control element, means -for synchroniz'ing the pulses produced by the transmitter with the range sweep and the range marker impulse generator, and a delay circuit interposed in advance of said beam control ele ment to delay the video input thereto for enabling the sweep to become linear before the receivedsignals are applied to the oscilloscope.

2. In a receiving apparatus for a micro-wave object locating system having a recurrent pulse transmitter, in combination', an oscilloscope having a deilectable beam and a beam-control element, means -for sweeping said beam in synchronism with said pulse transmitter, a video amplifier and a range marker signal generator adapted to supply received signals and marker signals to said beam control element, and a delay circuit connected from said video amplifier and said marker generator to said beam control element to delay the application oi video signals to .said oscilloscope.

' -for deilecting the beam of said device substantially linearly in synchronism with the recurrent intensity variations of said transmitter, said receiver having a video output coupled to said beam-intensity control grid, and delay means' interposed in said coupling to delay said video output to said beam-intensity control element until after the initiation of the beam deflecting means.

4. In combination, `a transmitter pulsing radiant energy, a receiver responsive thereto for producing receiver signal output, a deilectible beam device having a beam-control element, a sweep circuit therefor supplying a linear sweep wave in synchronism with pulse transmission from said transmitter, means supplying receiver signal output to said beam-control element,` and means for relatively advancing the sweep-wave and retarding said signal output supplied'to said control element.

5. In a pulse radio object detection system, in combination, means for periodically initiating signal pulses, means coupled to said pu1se-initiat ing means 4for transmitting toward a distant object radiant energy pulses synchronous with said initiated pulses, means for reproducing a variably delayed Version of said initiated pulses comprising a receiver for detecting radiant energy pulses reilected from said distant object, an. oscilloscope having a beam deflection circuit and a signal input circuit, means coupled to said beam deflection circuit and synchronized with said pulse initiating means for producing recurrent beam deections in said oscilloscope, means coupling said reproducing' means to said oscillescope signal input circuit for delivering thereto a variably delayed version oi said initiated-pulses l l and producing on said oscilloscope a pattern representing said variably delayed version of said initiated pulses, and means for introducing a predetermined further delay between initiation of said pulses and, delivery of said variably delayed version thereof to said oscilloscope' signal input circuit. Y

6. A system as defined in claim 5, wherein said last-named means comprises a leading gate generator, a main gate generator having a coupling for gating said receiver, said pulse initiating means having a delayed output, said gate generators being triggered by said pulse initiating means with the triggering of said leading gate generator relatively in advance with respect to the triggering of said main gate generator, and said transmitter being triggered by said trigger pulse generator relatively in retardment with respect to the triggering of said leading gate generator, and a coupling from said leading gate generator to said beam deflection producing means for synchronizing said beam deection means with said pulse initiating means.

7. A system as dened in claim 5, wherein said last-named means comprises a leading gate generator having a coupling to said oscilloscope for controlling the operation thereof, a main gate generator ior triggering said receiver, said signal generator. i

DAVID E. KENYON.

REFERENCES CITED The following references are ofirecord in the tile of this patent:

UNITED STATES PATENTS Number Name Date 2,158,285 Koch May 16, 1939 2,189,549 Hershberger Feb. 6, 1940 2,227,598 Lyman et al. Jan. '1, 1941 2,280,531 Norgaard4 Apr. 21, 1942 2,285,043 Messner June 2, 1942 2,345,932

Gould -.1 Apr. 4, 1944 

